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Pathogen Page

Marek's disease virus

I. General Information

1. NCBI Taxonomy ID:

2. Disease:

Marek's disease

3. Introduction

The causative agent of Marek’s disease. Gallid HV2 (Marek's disease virus)is highly contagious in chickens and induces T cell lymphomas in susceptible birds, causing annual losses to the worldwide poultry industry estimated at US$100 billion (Morrow and Fehler 2004). In the 100 years since Marek’s disease was first described, the disease has substantially increased in severity of symptoms. The first vaccines for gallid HV2 were developed in the late 1960’s and early 1970’s; but new, more virulent strains of the virus have emerged that are resistant to vaccine-induced immune responses (Nair 2005).

The virulence of gallid HV2 is expected to be a polygenic trait, with allelic variants at a number of loci playing a role (Shamblin et al. 2004). Thus, homologous recombination is expected to play an important role in the evolution of virulence, because it can bring together new mutations that originally evolved against different genetic backgrounds. DNA replication in alphaherpesviruses is recombination-dependent, providing a mechanism for homologous recombination between genetically distinct viruses infecting the same cell (Thiry et al. 2004). Sequence analysis has provided evidence of past homologous recombination events in several herpesviruses, including alphaherpesviruses (Bowden et al. 2004; Norberg et al. 2004; Peters et al. 2006) (Hughes and Rivailler, 2007).

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